One or more aspects of embodiments of the present disclosure are related to a material for an organic electroluminescent device and an organic electroluminescent device including the same, and more particularly, to a hole transport material for an organic electroluminescent device having high emission efficiency and a long lifespan, and an organic electroluminescent device including the same.
Organic electroluminescent (EL) image displays have been actively developed in recent years. Unlike liquid crystal displays and the like, organic EL displays are so-called “self-luminescent displays”, in which holes and electrons are respectively injected from anodes and cathodes into an emission layer, where they recombine and cause light to be emitted from a luminescent organic material in the emission layer, thereby displaying images.
An example organic EL device may include an anode, a hole transport layer on the anode, an emission layer on the hole transport layer, an electron transport layer on the emission layer, and a cathode on the electron transport layer. Holes from the anode may be injected via the hole transport layer into the emission layer. Electrons from the cathode may be concurrently (e.g., simultaneously) injected via the electron transport layer into the emission layer. The holes and the electrons injected into the emission layer may recombine to generate excitons within the emission layer. The organic EL device may emit light generated by radiative decay of the excitons. Organic EL devices are not limited to the above-described configuration, but may be produced in one or more suitable forms.
Display applications require organic EL devices having high efficiencies. However, organic EL devices in the blue light-emitting region require high driving voltages, and may therefore suffer from low emission efficiencies compared to organic EL devices in the green and red light-emitting regions. Previously attempted strategies for achieving organic EL devices with high efficiencies include normalization and stabilization of the hole transport layer and enhancement of durability.
Various organic EL devices in the related art have used aromatic amine-based compounds as hole transport materials in the hole transport layer. However, the emission efficiencies and lifespans of these devices have been limited. For example, an amine derivative having a substituent aryl group or heteroaryl group has been suggested as an material that may extend the lifespan of organic EL devices. However, organic EL device employing these amine derivative materials have not exhibited sufficient emission efficiencies and lifespans. Thus organic EL devices having improved lifespans are still highly desired.
Furthermore, although a compound in which fluorene is bound to the nitrogen atom of a monoamine through a phenylene linker is known to exhibit high hole transportability, there still remains a need for compounds with sufficiently high emission efficiencies and long lifespans.